A Methodology to Derive SPDY’s Initial Dictionary for Zlib Compression

This paper presents a methodology to derive an appropriate initial dictionary for SPDY to compress HTTP headers using the dictionary data compression method zlib. After applying our methodology, and by using our proposed initial dictionary, an additional 8% compression of the first HTTP request header and an additional 15% compression of first HTTP reply header on a SPDY connection is gained over SPDY’s current default initial dictionary. For the 2nd, 3rd, and further HTTP request (or reply) headers transmitted over the same SPDY connection, compression using our proposed initial dictionary is practically identical to that achieved by SPDY’s default initial dictionary. This result suggests zlib’s adaptive dictionary evolves to roughly the same state after compressing the first HTTP header regardless of the initial dictionary.